Compact steam reformer

ABSTRACT

A reformer ( 2 ) which enables rapid load changes of up to 100% within a few seconds, and which is intended to produce hydrogen from hydrocarbons by steam reformation, has an evaporator cooler for cooling the reformate and for generating steam. The evaporator cooler ( 34 ) is disposed in the reformer ( 2 ), on the end of its reaction vessel. It keeps the applicable end of the tube cool and uses the waste heat of the reformate for generating steam. This makes fast load changes possible, because an increase in the introduction of water immediately causes an increase in the reformate produced and thus an increase in the heat output.

[0001] The invention relates to a reformer for producing hydrogen,having the characteristics of the preamble to claim 1, and to a methodfor producing hydrogen from water and hydrocarbon compounds.

[0002] For hydrogen generation, steam and a hydrocarbon compound(C_(x)H_(y), organic compound, hydrocarbon mixture) are made to react athigh temperature in a catalytic converter.

[0003] From European Patent Disclosure EP 0 848 989 A2, a co-current orcountercurrent reactor is known which includes a monolithic element withmany conduits parallel to one another, which are divided into two groupsinternested with one another. The reactands (educts) flow through onegroup, while a mixture of combustion gas and air flows through theother.

[0004] If steam is among the reactands, then it must be generatedseparately.

[0005] From U.S. Pat. No. 5,484,577, a reformer with a combustionchamber that is heated via a gas burner is known. A substantiallycylindrical reaction vessel is disposed in the combustion chamber, andits outer jacket is heated by the gas flame produced and by the hotcombustion gases. Catalyst pellets are disposed in an outer ring regionin the reaction vessel. The reaction gas mixture flows through thecatalyst pellets and through a cylindrical return conduit to the gasoutlet.

[0006] The reactands are delivered in the form of gas or steam.

[0007] This is also true for the reformer of U.S. Pat. No. 5,811,065,which combines a plurality of reformers into a reformer battery.

[0008] In recent times, small reformer systems with a capacity of about1 to 200 Nm³/h of hydrogen are needed for producing hydrogen as processgas or protective gas and to generate current using fuel cells. In suchcompact reformers, attempts to optimize the thermal economy are made invarious ways.

[0009] The use of reformers to produce hydrogen for fuel cells,especially in small power plants with a capacity in the range from 5 kWto 20 kW, necessitates fast adaptation of the water production to loadchanges. The hydrogen yield should be equivalent to that of largesystems. If natural gas is used as the starting gas, this meansapproximately 2.5 to 2.7 m³ of hydrogen, per m³ of natural gas. This isequivalent to an efficiency for energy conversion of 75 to 80%, in eachcase referred to the lower calorific value.

[0010] It is the object of the invention to create a compact reformer.

[0011] The reformer according to the invention meets this requirement.The reformer generates hydrogen from water and methane or otherhydrocarbons in the form of steam (gaseous state) at elevatedtemperature in a catalytic converter. For evaporating water, anevaporator cooler is provided. Water supplied is extensively evaporatedin the evaporator cooler using the heat of the outflowing reactionproducts (reformate).

[0012] The flow rates of the products and educts are necessarily thesame. Any change in evaporation output upon a load change causes acorresponding change in the flow rate of reformate—and correspondingly,the power input into the evaporator cooler changes. All the streams ofmaterial into the reaction vessel and out of it are alwayschronologically synchronous, and load-guided evaporation is thus madepossible. The thermal inertia of the reaction vessel and the responsetime for the burners for varying the heating output does not have aninhibiting effect on the speed of load changes. On the contrary; upon asudden change in load, the thermal inertia of the reaction vessel actsas a heat buffer, without which an especially fast load change is noteven possible. Load changes of 100% can be attained within a fewseconds.

[0013] The evaporation of the water and optionally of the fuel takesplace at the inlet to the reformer, essentially by means of thereformate to be cooled down. Only a fraction of the requisite heat isdrawn as needed from the exhaust gas of the burner, and as a result theevaporator temperature can be regulated.

[0014] The evaporator cooler is preferably embodied as a splitevaporator, in which the inlet conduit and the outlet conduit areembodied as helical split conduits. The inlet conduit is embodiedpreferably between the inside wall face of the reaction vessel and aninsert body. The outlet conduit preferably leads along the inside wallface of the insert body. Water and fuel are preferably delivered intothe common inlet conduit via capillaries. Thus a mixture of water andfuel is evaporated. The fuel can be in gaseous or liquid form. Atomizereffects that occur reinforce the evaporation.

[0015] The reaction vessel is preferably embodied such that even at hightemperatures (for instance, up to 1000° C.), it withstands highpressures (such as 10 or 20 bar). To that end, it is preferably embodiedas a cylindrical pressure vessel. It enables the discharge of hydrogenunder pressure for performing gas cleaning, for instance by a membraneprocess; recompression can be dispensed with. Because of the lesservolume of the educts, the compression on the delivery side of thereformer can be achieved with substantially less compressor energy (by afactor of 5) than in the case of recompression downstream of thereformer.

[0016] The evaporator is heated primarily by the reformate. In addition,exhaust gas heating can be done through the wall of the reaction vessel.This makes it possible to regulate the evaporator temperature precisely.Preferably over 90% of the evaporator output is supplied from thethermal energy of the reformate. Only some of the heat of evaporation issupplemented by thermal conduction of the reaction vessel and by apartial flow of exhaust gas. As a result, even upon startup of thesystem or during idling, the evaporator cooler can be kept at thedesired temperature. To that end, a regulating device (temperatureregulator) can be provided in a suitable conduit for a partial flow ofexhaust gas, extending for instance along the outside face of thereaction vessel. The efficiency of energy conversion is as high as 80%,or more.

[0017] The heat exchanger is preferably disposed in the pressure vessel,so that virtually the same pressures prevail in both the inlet conduitand the outlet conduit. The heat exchanger is thus force-neutral.

[0018] The burner for heating the reaction vessel is preferably a burnerthat utilizes the exhaust gas heat, such as a recuperator burner or aregenerator burner. The burner can be regulated on the basis of thecombustion chamber temperature. There is accordingly an automaticadaptation to the heat demand of the reformer at the time. Temporarydifferences between the heat demand and heat delivery are compensatedfor by the heat stored in the reformer.

[0019] The combustion chamber can be arranged for flameless oxidation.To that end, small-area eddies and circulations that could serve todevelop and maintain flames are avoided. Low-NO_(x) and low-wearoperation thus results. Furthermore, fluctuations in the calorific valueof the combustion gas are not critical.

[0020] In a preferred embodiment, one or more reaction vessels and oneor more burners are disposed concentrically to one another. Forinstance, one centrally disposed burner is surrounded by a plurality ofreaction vessels. Conversely, one reaction vessel can be surrounded by aplurality of burners or can receive them in a recess. In both cases, thereaction vessel or vessels and the burner or burners are introduced fromone side into a preferably cylindrical chamber of the housing. Thismakes for a compact embodiment of the entire apparatus and makessimplified regulation possible. For instance, regulating the partialflows of exhaust gas for adaptation to different load situations can bedispensed with. Heat losses can also be reduced.

[0021] The reaction vessel can be embodied as ceramic, which stillfurther increases the wear resistance to corrosion at high temperaturessubstantially. In a preferred embodiment, it has a slenderer partprotruding into the combustion chamber, in which part the actualreforming process takes place at between 700 and 1200° C. If needed, itcan have a portion of greater diameter, which creates space forcatalytic converters for the prereforming process (300 to 500° C.) forsplitting or cracking long-chain C_(x)H_(y) into CH₄ and receives theevaporator cooler. The evaporator cooler is preferably embodiedannularly. Its interior, which is at a temperature between 200 and 400°C., a catalytic converter for performing a shift reaction or a membranefilter on the outlet side for trapping carbon monoxide can be disposed.

[0022] The evaporator cooler enables fast, on-demand evaporation of thewater and optionally fuel. Water, as long as it is liquid, keeps theevaporator below its pressure-dependent boiling temperature of 100 to180° C. This on the other hand makes a shocklike cooling down of thereformate (quench cooling) possible. As a result, soot development,which occurs on surfaces at temperatures between 400 and 600° C., isstrictly avoided.

[0023] Further details of advantageous embodiments of the invention arethe subject of the drawing and the ensuing description.

[0024] In the drawing, exemplary embodiments of the invention are shown.Shown are:

[0025]FIG. 1, a reformer system with a reformer, in a schematiclongitudinal section;

[0026]FIG. 2, a modified embodiment of the reformer of FIG. 1;

[0027]FIG. 3, a modified embodiment of a reformer with heating byregenerative burners, shown schematically;

[0028]FIG. 4, a reformer with a ceramic reformer tube and a shiftreactor;

[0029]FIG. 5, a reformer with a ceramic reformer tube and a separationmembrane body, shown schematically and partly in section;

[0030]FIG. 6, a modified embodiment of a reformer, in a schematiclongitudinal section;

[0031]FIG. 7, the reformer of FIG. 6, shown in cross section;

[0032]FIG. 8, a further embodiment of the reformer, in a schematiclongitudinal section; and

[0033]FIG. 9, the reformer of FIG. 8, in a schematic cross section.

[0034]FIG. 1 shows a reforming system 1 with a reformer 2 for generatinghydrogen from fuel and water. The reformer 2 is followed downstream by aPSA 3 (for pressure swing adsorption system) for separating out CO. ThePSA 3 has a plurality of adsorption columns 4, through which thereformate periodically flows and is back-flushed. Residual gases aredelivered to the reformer 2 via a line 5.

[0035] The reformer 2 has a housing 6, for instance cylindrical, with aheat insulation jacket 7. This jacket encloses a heating or combustionchamber 8, which for instance is cylindrical, on the face end 9 of whicha burner 11 is disposed. The burner 11 is connected both to the line 5and to a fuel line 12. Via a line 14, air is delivered to the burner 11.Exhaust gases leave the burner 11 via an exhaust gas line 15. The burner11 has a recuperator 16, which on the outside defines an annular exhaustgas conduit 17 and on the inside defines an air delivery conduit 18. Therecuperator 16 serves to utilize the heat of the exhaust gas. This heatis transmitted to the incoming air and optionally to the fuel.

[0036] On the face end 19 of the combustion chamber 8 opposite theburner 11 (the lower face end), the insulating jacket 7 has acylindrical passage 21, in which a chemical reactor 22 is disposedcoaxially to the burner 11; this reactor protrudes into the combustionchamber 8. The reactor 22 has as its reaction vessel a tube 23, closedon one end, for instance of heat-resistant steel or some other suitablematerial, whose closed end points toward the burner 11. In a departurefrom this, the burner 11 can instead be disposed at any arbitrarysuitable point of the combustion chamber 8.

[0037] The tube 23 is secured by its open end to a head 24, by way ofwhich the educts are delivered and the products are carried away. Thispurpose is served by a line 25, which via a water pump 26 is acted uponby water at the desired pressure (such as 10 bar) and in the desiredquantity, and by a line 27 for fuel. The latter line communicates withthe fuel line 12, and a fuel pump 28 serves to pump fuel into thereactor 22 in the desired quantity and at the desired pressure (10 bar).On the head 24, a reformate line 29 is provided, which leads to the PSA3 via a reformate cooler 31. An exhaust gas 32 with a regulating valve33 (such as a thermostat valve) is also provided on the head 24, and byway of it exhaust gas from the combustion chamber 8 can be carried asneeded to the outside via an annular-gaplike conduit 34 along the tube23.

[0038] In the tube 23, immediately adjacent the head 24, there is anevaporator cooler 35 serving as an evaporator. It includes a tubularbody 36, which is provided on its outside with one or more shallowthread courses and whose outside together with the inner wall of thetube 23 defines an inlet conduit 37. This inlet conduit carries theeducts into a gaplike, helical conduit and then along the outer jacketface of an annular heat insulation element 38 into the reaction chamberof the reactor 22, in which there is a catalytic converter 39. Thecatalytic converter 39 fills the reaction chamber virtually completely.It has a central conduit, through which a collector tube 41 leads backto the evaporator cooler 35. The collector tube is provided, on its endprotruding through the catalytic converter 39, with gas inlet openingsand is otherwise closed. It discharges into the interior of theevaporator cooler 35, in which an insert body 42 is provided. Theapproximately cylindrical jacket face of the insert body, together withthe inner wall of the evaporator cooler 35, defines a gaplike andpreferably helically coiled outlet conduit 43, which leads to thereformate line 29.

[0039] The reforming system 1 described thus far is especially suitablefor generating hydrogen in the range from 1 to 200 m³/h. It functions asfollows:

[0040] In operation, the combustion chamber 8 is kept by the burner 11at a temperature of 800° C. to 1200° C. The exhaust gases flowing outvia the exhaust gas conduit 17 heat the combustion air, flowing incountercurrent in via the air delivery conduit 18, to up to 800° C.,thus utilizing the exhaust gas heat. A flame can develop in thecombustion chamber. If small-area eddies are avoided, flamelessoxidation can also be achieved.

[0041] The end of the tube 23 protruding-into the combustion chamber 8and the catalytic converter 39 are thus heated to a temperature between700° C. and 1200° C. The mixture of water (H₂O) and fuel (CH₄ orC_(x)H_(y)) flowing through here reacts predominantly to producehydrogen, carbon monoxide, carbon dioxide, and water steam. Residues ofthe fuel can also still be contained in the reformate, which is nowcarried through the collector tube 41, through a central opening in theheat insulation element 38, to the evaporator cooler 35. The reformatearrives there essentially still uncooled, that is, at the sametemperature with which it left the catalytic converter 39 (that is,markedly above 600° C.). At this temperature, it enters the outletconduit 43. Because the evaporator cooler 35 is kept in its entirety ata temperature of hardly more than 200° C. by the liquid water (which at10 bar does not boil until 180° C.) flowing through the inlet conduit 37and countercurrent, the reformate entering the outlet conduit 43experiences shock cooling (quench cooling). It passes through thetemperature range from 500 to 600° C. very quickly, so that virtually nosoot formation from decomposition of CO occurs. Its thermal content isutilized for countercurrent water evaporation. The cooled reformateleaves the reactor 22 via the reformate line, is cooled down furthersomewhat in the reformate cooler 31 for water separation, and at thereactor pressure of about 10 bar enters the respective adsorptioncolumns 4 that have been switched to be active. If such a column issaturated with the remaining carbon monoxide, it is back-flushed. Inthis way, the CO is carried via the line 5 to the burner 11. Thisprocess is known as pressure change absorption. Cleaned hydrogen leavesthe reforming system 1 via an outlet line 44.

[0042] Sudden changes in the need for hydrogen necessitate a suddenchange in the pumping by the water pump 26 and the fuel pump 28. As aresult, the flow rate both into the inlet conduit 37 and into the outletconduit 43 are changed, in accordance with the load change. As a resultof the change in throughput in the outlet conduit 43, the evaporatoroutput is immediately adapted in the inlet conduit 37. The steamgeneration thus responds without delay to the altered demand for steam.Conversely, the regulation of the burner 11 can be substantially slowerwithout impairing the capacity of the reforming system 1. It sufficesfor the burner 11 to be regulated such that the combustion chamber 8 iskept at an adequately high (constant) temperature.

[0043] The water (and liquid fuel if applicable) is evaporated in theinlet conduit 37 in countercurrent to the outflowing reformate. The coldwater in the inlet conduit also directly cools the tube 23 and thusavoids heat conduction losses. The thermal content of the reformatecovers the great majority of the heat flow required for waterevaporation.

[0044] For instance, the balance is as follows:   1 Nm³/h CH₄; 20 → 200°C.: −0.088 kW 1.6 kg/h H₂O; 20 → 200° C. (includes evaporation) −1.237kW −1.325 kW   5 Nm³/h reformate, 900 → −300° C. +1.237 kW

[0045] The missing amount of 0.088 kW (approximately 7%) is partlycompensated for by thermal conduction in the reformer tube and by alesser partial flow of exhaust gas from the heating chamber.

[0046] The partial flow of exhaust gas is regulated for instance by athermostat valve in the exhaust gas line 32. The partial flow of exhaustgas has significance particularly for starting up the reforming system1. Upon startup, it furnishes the requisite evaporation energy for thewater, as long as a sufficient reformate flow is present. After that,the exhaust gas leaves the combustion chamber 8 predominantly throughthe exhaust gas conduit 17.

[0047] In FIG. 2, a modified embodiment of the invention is illustrated.To the extent that it matches the reforming system 1 described above,reference is made to the above description, using the same referencenumerals. The reformer 2 a shown in FIG. 2 has an enlarged combustionchamber 8, into which a plurality of reactors 22 protrude, for instancearranged in a circle that is concentric with the burner 11. Each reactor22 has its own evaporator—in this respect, it is a complete unit byitself. These units function as described above. The reforming system 1is constructed in modular fashion. Combining a plurality of reactors 22into a reactor battery opens up the possibility of covering a broadcapacity spectrum, using uniform reactors 22, by suitable adaptation oftheir number (building-block principle). The design of the combustionchamber, as indicated by arrows 46 in FIG. 2, makes it possible toachieve large-area recirculation, so that heat generation by flamelessoxidation is made possible.

[0048] As FIG. 3 also shows, the burner 11 can alternatively be designedas a regenerative burner. In an otherwise identical embodiment, thisreformer 2 b has two regenerators 47, 48, through which exhaust gas andair flow in alternation and in counterpoint. The control is performed byan exhaust gas-air switchover valve 49. In the starting mode, the fuelis delivered via fuel lines 12, which lead through the regenerators 47,48. The residual gas is fed directly into the combustion chamber 8 viathe line 5 and oxidates without flame. The reformer 2 b makes especiallygood utilization of the fuel energy possible.

[0049] It is also possible, instead of the tube 23, to provide a forinstance cylindrical ceramic reformer tube. It can also take the form ofthe reformer tube 51 (see reformer 2 c in FIG. 4, with a metal orceramic tube). The preference for ceramic is because of its high wearresistance at high temperature. As FIG. 4 shows, an upper portion,containing the catalytic converter 39, can have a lesser diameter thanthe rest of the reformer tube 51. Only the slenderer portion is exposedto the direct heating. A heat shield 52 is disposed in a conicaltransitional region of the reformer tube 51, to prevent uncontrolledheating of the remainder. The heat shield 52 is a heat-insulating ring,which with the reformer tube 51 encloses a split conduit. The splitconduit changes over into the annular-gaplike conduit 34, which leads tothe thermostat regulator 33.

[0050] In the widened portion of the reformer tube 51, a prereformingcatalytic converter can be disposed immediately above the evaporatorcooler 35; it can serve to split longer-chain hydrocarbons into methanein the temperature range from 300° C. to 500° C. Thus the reformer 2 cis especially suitable for liquid hydrocarbons, which are delivered viaa capillary conduit (line 27). Also, as in all the embodiments, water(line 25) is sprayed into the common inlet conduit 37 via a capillaryconduit, so as to be evaporated in the inlet conduit jointly with thefuel.

[0051] The reformer 2 c additionally includes a shift catalyticconverter 55, which serves the purpose of postoxidation of carbonmonoxide and water to form carbon dioxide and hydrogen. The shiftcatalytic converter 55 is disposed in an inner chamber 56 enclosed bythe insert body 42. This chamber communicates directly with the outletconduit 43. The shift catalytic converter is housed by a sleeve and aperforated bottom 57 in such a way that the reformate is compelled toflow through it.

[0052] The reformer tube 51 is retained on the head 24 with an annularflange. As a consequence of the cooling by the inflowing water, thisflange is relatively cool. Elastic seals can be employed.

[0053] Instead of the shift catalytic converter 55, it is possible, asshown in FIG. 5, in a corresponding reformer 2 d, for a separationmembrane 59 (palladium-silver) to be provided, retained on one or moresupport tubes 58. This membrane can serve to separate out CO, and hereit finds the appropriate temperature. Residual gas is removed from theinner chamber 55 through a separate residual gas conduit 60 and isreturned for instance to the burner 11 again. The residual gas conduitis disposed at the base of the separation membrane 59. For preventingthe reformate from flowing into the residual gas conduit 60, a tubularsleeve 61 is provided, which like the separation membrane 59 protrudesupward from the bottom of the head 24 and together with the separationmembrane 59 defines an annular gap.

[0054] A further embodiment of the invention is shown in FIGS. 6 and 7.The description provided for FIG. 1 above applies accordingly in termsof the same reference numerals. However, the reformer 2 of FIG. 6differs from the reformer of FIG. 1 as follows:

[0055] Only at the face end 19 of the combustion chamber 8 does theinsulating jacket 7 have the passage 21, through which both the reactor22 and burners 11 a-11 h (FIG. 7), which form a burner group 111,protrude into the interior of the insulating jacket 7. The reactor 22 isembodied as a double-walled, cup-shaped vessel with an outer wall 22 aand an inner wall 22 b, which are disposed concentrically to oneanother. The space between the two cup-shaped walls 22 a, 22 b forms thereactor interior. This interior is divided into an annular inflowconduit (inside) and an annular outflow conduit (outside) by a tubularwall 141, which is seated concentrically between the outer wall 22 a andthe inner wall 22 b and which extends over virtually the entirecylindrical length of the reactor 22. The catalytic converter 39 isseated between the inner wall 22 b and the wall 141. The wall 141 formsa heat exchanger wall, at which the products and educts exchange heat incountercurrent.

[0056] The outer wall 22 a, the inner wall 22 b, and the wall 141 aresecured to retaining rings 101, 102, 103, which rest on one another andare stacked axially one above the other. Each retaining ring 101, 102,103 is provided with an annular groove 104, 105, 106, which serves as afluid conduit and communicates via a gap with the respective internalvolume connected to it. To that end, each retaining ring 101, 102, 103is higher in the axial direction on the outside than on the inside. Thereformate line 29 leads into the annular groove 104. The line 25 leadsinto the annular groove 105, and the exhaust gas line 32 leads into theannular groove 106. This last groove communicates with the interior thatis enclosed by the cup-shaped inner wall 22 b. This interior at the sametime forms the combustion chamber 8, in which the burners 11 a-11 h aredisposed concentrically to a longitudinal center axis A. A guide tube107 is disposed in the combustion chamber 8, and its diameter is lessthan the diameter along which the burners 11 a-11 h are disposed. Thisforces a large-area recirculation flow to occur in the combustionchamber 8, for the sake of enabling flameless oxidation.

[0057] The burners 11 a-11 h are embodied identically to one another.They each have a recuperator tube 109, which tapers toward its orificeand is retained on its end on a retaining ring 108, and whose internalconduit is connected, via an annular groove 110, to the line 14 fordelivering air and brings about the heat exchange between exhaust gasesand fresh air in countercurrent. On the inside, each recuperator tube109 encloses a fuel delivery tube 112. This tube is secured in aretaining ring 114, which forms a stack with the other retaining rings101, 102, 103, 108. Toward the outside, the stack is covered by arelatively thick insulating disk 115. A temperature sensor 116 and anignition burner 117 extend into the combustion chamber 8 through theinsulating disk 115 and the stack of retaining rings.

[0058] The special feature of this embodiment is that the combustionchamber 8 is enclosed by the reactor 22. An inner chamber 8 a enclosedby the insulating jacket 7 in turn encloses the reactor 22, but its walldoes not have any direct contact with the hot combustion gases. Theheat-insulating housing can thus be constructed economically. It hasbeen demonstrated that this embodiment is advantageous especially at avery low reformer output, for instance of less than 1 Nm³ of H₂/h.Experiments have shown that in this arrangement, regulating the partialflows of exhaust gas to supplement the evaporator output (see regulatingvalve 33 in FIG. 1) can be dispensed with.

[0059] A further embodiment of the reformer 2 of the invention is shownin FIGS. 8 and 9. While the reformer of FIG. 6 has internal heating, thereformer of FIG. 8 is provided with external heating. The reactor 22,which is constructed similarly to FIG. 1, is surrounded, as FIG. 9particularly shows, by burners 11 a-11 h. These are constructedbasically as in FIG. 6. Their recuperator tubes 16 end in a nozzle forgenerating a large-area recirculation flow. To carry this flowappropriately into the combustion chamber 8, a guide tube 118 isdisposed in the combustion chamber, concentric with the reactor 22.Otherwise, with the same reference numerals, reference may be made tothe various descriptions above. The ignition burner 117 is disposedlaterally at a radial opening in the insulating jacket 7 and thusdischarges radially into the combustion chamber 8.

[0060] This embodiment of the reformer 2 is likewise compact andespecially suitable for small outputs. Regulation of a partial flow ofexhaust gas that supplements the evaporator output can be dispensedwith.

[0061] A reformer 2 which enables fast load changes of up to 100% withinonly a few seconds, and which is intended to produce hydrogen by steamreformation from hydrocarbons, has an evaporator cooler for cooling thereformate and for generating steam. The evaporator cooler 34 is disposedin the reformer 2, on the end of its reaction vessel. It keeps theapplicable tube end cool and uses the reformate waste heat forgenerating steam. Fast load changes are also possible because anincrease in the introduction of water immediately also causes anincrease in the reformate produced and thus an increase in the heatoutput.

1. A reformer (2) for producing hydrogen from a hydrocarbon compound andwater, having a thermally insulated heating chamber (8), with which atleast one heat source is associated, having at least one reaction vessel(23), which extends into the heating chamber (8) and leading into whichis at least one inlet conduit (37) and leading out of which is at leastone outlet conduit (43), characterized in that the inlet conduit (37)and the outlet conduit (43) lead through an evaporator (35).
 2. Thereformer of claim 1, characterized in that the inlet conduit (37) isembodied as a threaded split conduit, and that the outlet conduit (43)is embodied as a threaded split conduit.
 3. The reformer of claim 1,characterized in that the inlet conduit is embodied between the innerwall of the reaction vessel (23) and an evaporator body (35).
 4. Thereformer of claim 1, characterized in that the reaction vessel (23) is apressure vessel.
 5. The reformer of claim 1, characterized in that theevaporator (35) is disposed in the reaction vessel (23).
 6. The reformerof claim 1, characterized in that the evaporator (35) is heated by aregulated partial flow of exhaust gas.
 7. The reformer of claim 1,characterized in that the burner (11) is a recuperator burner or aregenerator burner.
 8. The reformer of claim 1, characterized in thatthe reaction vessel (51) is embodied of ceramic.
 9. The reformer ofclaim 1, characterized in that between the evaporator (35) and areforming catalytic converter (39), there is a prereforming catalyticconverter (54) for splitting higher hydrocarbons.
 10. The reformer ofclaim 1, characterized in that a hydrogen separation membrane (59) isdisposed on the outlet side of the evaporator (35).
 11. The reformer ofclaim 1, characterized in that the burner (11) and the reaction vessel(23) are disposed concentrically to one another.
 12. The reformer ofclaim 1, characterized in that the burner (11) and the reaction vessel(23) protrude through a common opening into the heating chamber (8). 13.A method for producing hydrogen in a steam reforming process from waterand a hydrocarbon compound, in which water is evaporated, utilizing theheat contained in the reformate produced.
 14. The method of claim 13,characterized in that the water and the hydrocarbon compound areevaporated as a common stream of material.